1. Field of the Invention
The present invention relates generally to an operation for configuring a Transport Format Combination Set (TFCS) in a mobile communication system. More particularly, the present invention relates to a method and apparatus for efficiently transmitting and receiving control information required to configure a TFCS.
2. Description of the Related Art
Today's mobile communication systems are evolving toward high-speed, high-quality wireless data packet communication systems that provide data service and multimedia service beyond voice-oriented service provided at the early stage of system development.
In Universal Mobile Telecommunication Services (UMTS), a 3rd generation mobile communication system uses Wideband Code Division Multiple Access (WCDMA) based on the European mobile communication systems, Global System for Mobile communications (GSM) and General Packet Radio Services (GPRS). When a User Equipment (UE) or a Node B transmits data on a physical channel, the UE or Node B simultaneously transmits a Transport Format Combination Indicator (TFCI) indicating how the data was multiplexed. A TFCS is a set of Transport Format Combinations (TFCs) providing information regarding data multiplexing. The TFCs are identified by their TFCIs. The TFCS is configured at call setup and the configuration information of the TFCS is exchanged between a UE and a Radio Network Controller (RNC). If the TFCS configuration information is bulky, the time taken for the call setup is increased, leading to increased consumption of radio transmission resources.
FIG. 1 illustrates the configuration of a typical mobile communication system, UMTS herein.
Referring to FIG. 1, the mobile communication system includes a Core Network (CN) 100 and a plurality of Radio Network Subsystems (RNSs) 110 and 120. The RNSs 110 and 120 form a UMTS Terrestrial Radio Access Network (UTRAN). The CN 100 includes a Serving GPRS Support Node (SSGN) and a Gateway GPRS Support Node (GGSN) to connect the UTRAN to a packet data network such as the Internet.
The RNSs 110 and 120 have RNCs 111 and 112 and a plurality of Node Bs 113 to 116. For example, the RNC 110 includes the RNC 111 and the Node Bs 113 and 115, and the RNS 120 has the RNC 112 and the Node Bs 114 and 116. The RNCs 111 and 112 are classified into a serving RNC, drift RNC and controlling RNC according to their roles. The serving RNC manages information regarding UEs and is responsible for data transmission to and reception from the CN 100. The drift RNC is directly connected to a UE 130 wirelessly. The control RNC controls the radio resources of the Node Bs 113 to 116.
The RNCs 111 and 112 are connected to the Node Bs 113 to 116 via Iub interfaces. An Iur interface is defined between the RNCs 111 and 112. While not shown, the UE 130 is connected to the UTRAN via a Uu interface. The RNCs 111 and 112 allocate radio resources to the Node Bs 113 to 116 under their management, and the Node Bs 113 to 116 provide the allocated resources to the UE 130. The radio resources are configured on a cell basis and the radio resources of each Node B are resources of a particular cell managed by the Node B. The UE 130 establishes radio channels with the radio resources of cells managed by the Node Bs 113 to 116, and transmits and receives data to and from the cells on the radio channels. Since the UE 130 identifies only a physical channel configured on a cell basis, the distinction between Node B and cell is meaningless. Therefore, the terms “Node B” and “cell” are interchangeably used below.
FIG. 2 illustrates a hierarchical protocol architecture for the typical mobile communication system.
Referring to FIG. 2, the Uu interface is divided into a control plane (C-plane) 200 for exchanging control signals between the UE and the RNC and a user plane (U-plane) 202 for transmitting user data between the UE and RNC.
A Radio Resource Control (RRC) layer 204, Radio Link Control (RLC) layer 210, Medium Access Control (MAC) layer 214, and physical (PHY) layer 218 reside on the C-plane 200. On the U-plane 202, there are a Packet Data Convergence Protocol (PDCP) layer 206, Broadcast/Multicast Control (BMC) layer 208, RLC layer 210, MAC layer 214, and the PHY layer 218.
The PHY layer 218 provides an information delivery service by a radio transfer technology, corresponding to Layer 1 (L1) in the Open System Interconnection 7 (OSI 7) model. The PHY layer 218 is connected to the MAC layer 214 via transport channels (TrCHs) 216. Data is exchanged between the MAC layer 214 and the PHY layer 218 via the TrCHs 216. The Transport Formats (TFs) of the TrCHs 216 are determined according to how data is processed in the PHY layer 218. A set of TFs defined for one TrCH is called a Transport Format Set (TFS).
Table 1 below illustrates an exemplary TFS.
TABLE 1Semi-Static PartDynamic PartTTI = 20 msecTF 00x148 bitChannel Coding = CC, ⅓TF 11x148 bitRM = 155TF 22x148 bit
As noted from the above Table 1, TF has two properties: semi-static part and dynamic part. The semi-static part is a property common to all TFs defined for a TrCH, inclusive of a Transmission Time Interval (TTI), channel coding and coding rate, and Rate Matching (RM) parameter.
The dynamic part is divided into a transport block size and a transport block set size. The dynamic part is different for each TF. The transport block is a data unit transmitted on a TrCH. In Table 1, one transport block has 148 bits.
The transport block set is the number of transport blocks transmitted for one TTI. In Table 1, the transport block set size is 1 for TF 1, which means that one block of 148 bits is transmitted for 20 msec.
A plurality of TrCHs can be multiplexed in one physical layer. Thus, data transmitted on the physical channel at a particular time instant can be expressed as a set of the TFs of the multiplexed TrCHs. If three TrCHs are multiplexed in the manner that Transport Channel 1=TF 0, Transport Channel 2=TF 2, Transport Channel 3=TF 1, the set of TFs is a TFC.
The UE and the RNC together preset available TFCs during call setup. The set of TFCs is a TFCS.
The MAC layer 214 delivers data received from the RLC layer 210 on logical channels 212 to the PHY layer 218 on appropriate TrCHs 216, and delivers data received from the PHY layer 218 to the RLC layer 210 on appropriate logical channels 212. The MAC layer 214 inserts additional information in data received on the logical channels 212, or interprets inserted data in data received on the TrCHs 216 and controls random access.
The MAC layer 214 is connected to the RLC layer 210 via the logical channels 212. The MAC layer 214 is divided into a plurality of sublayers. The RLC layer 210 is responsible for establishing and releasing the logical layers 212.
Typically for transmission, the RLC layer 210 segments, concatenates, or pads RLC Service Data Units (RLC SDUs) received from a higher layer to an appropriate size. The RLC layer 210 then constructs RLC SDUs by inserting information regarding the segmentation/concatenation/padding and sequence numbers into the RLC SDUs and transmits the RLC SDUs to a lower layer.
For reception, the RLC layer 210 Unacknowledged Mode (UM) re-constructs RLC SDUs by interpreting the sequence numbers and information regarding the segmentation/concatenation/padding of RLC SDUs received from the lower layer and transmits SDUs to the higher layer. The PDCP layer 206 resides above the RLC layer 210. The PDCP layer 206 is responsible for compression and decompression of a header of data carried in the form of an Internet Protocol (IP) packet and data delivery with integrity for where a serving RNC is changed due to the UE's mobility. The BMC layer 208 is also above the RLC layer 210. The BMC layer 208 supports the broadcast service of transmitting the same data to unspecified many UEs within a particular cell. The RRC layer 204 allocates or release radio resources between the UTRAN and the UE.
The UE and the RNC establish the TrCHs during call setup. This is the process of notifying the UE of the TFCs of the TrCHs and TFCS configuration information by the RNC, and establishing the TrCHs and configuring the TFCS correspondingly by the UE.
FIG. 3 is a diagram illustrating a signal flow for exchanging control messages for establishing TrCHs.
Referring to FIG. 3, an RNC 310 transmits a TrCH establishment message 315 to a UE 305. The TrCH establishment message 315 is a general message delivering TrCH-related control information, for example, Radio Bearer Setup or Transport Channel Reconfiguration.
The TrCH establishment message 315 includes TrCH configuration information 320 and TFCS configuration information 325. The TFCS configuration information 325 has TFC-Calculated Transport Format Combination (CTFC) mapping information 330.
The UE 305 configures TrCHs and a TFCS based on the received information 320 and 325, and transmits a Response message 340 to the RNC 310. Then the UE 305 and the RNC 310 transmit/receive data on the TrCHs.
FIG. 4 is a flowchart illustrating an operation for configuring a TFCS in the UE.
Referring to FIG. 4, the UE configures a TFCS based on TrCH configuration information and TFCS configuration information. Upon receipt of the TrCH configuration information in step 405, the UE calculates CTFCs based on the TrCH configuration information in step 410. The CTFCs are all available combinations of TFs for different TrCHs. In step 415, the CTFCs are mapped to TFCs based on TFC-CTFC mapping information set in the TFCS configuration information.
The TFCS configuration will be described in great detail with reference to FIGS. 5A, 5B and 5C. It is assumed that three TrCHs are configured for the UE. The semi-static part of each TrCH is not shown for clarity and conciseness.
The TFs of each TrCH are configured as illustrated in FIG. 5A. Three TFs are available for Dedicated CHannel 1 (DCH 1), two TFs for DCH 2, and two TFs for DCH 3. DCH x means a DCH with transport channel identifier x.
The UE calculates CTFCs using the TFs of the TrCHs. For example, the UE arranges the TrCHs in an identifier order and the TFs of a TrCH with a low identifier are arranged in an ascending order with respect to any of the TFs of a TrCH with a high identifier. The resulting combinations of the TFs of the TrCHs are CTFCs and the UE allocates identifiers to the CTFCs in order. Hence, CTFC n is a CTFC with identifier n. The CTFC calculation basically seeks to obtain all possible combinations of the TFs of the TrCHs.
The CTFC calculation is shown in FIG. 5B. The UE maps the TFs of DCH 1 in the order of the lowest TF to the highest TF, TF 0 to TF 2 to the lowest TF, TF 0 of DCH 2 and DCH 3. The resulting CTFCs are CTFC 0, CTFC 1 and CTFC 2.
The UE then maps the TFs of DCH 1 in the order of the lowest TF to the highest TF, TF 0 to TF2 to the second lowest TF, TF 1 of DCH 2 and the lowest TF, TF 0 of DCH 3. The resulting CTFCs are CTFC 3, CTFC 4 and CTFC 5.
The UE maps the TFs of DCH 1 in the order of the lowest TF to the highest TF, TF 0 to TF 2 to the lowest TF, TF 0 of DCH 2 and the second lowest TF, TF 1 of DCH 3. The resulting CTFCs are CTFC 6, CTFC 7 and CTFC 8.
The UE maps the TFs of DCH 1 in the order of the lowest TF to the highest TF, TF 0 to TF 2 to the second-lowest TF, TF 1 of DCH 2 and the second lowest TF, TF 1 of DCH 3. The resulting CTFCs are CTFC 9, CTFC 10 and CTFC 11.
After the CTFC calculation using the TFs of the TrCHs, the UE performs TFC-CTFC mapping which is the process of determining a combination of TFs for a particular TFC. Accordingly, signaled CTFCs are mapped sequentially to TFCs.
The TFC-CTFC mapping is carried out based on the TFC-CTFC mapping information set in the TFCS configuration information. The TFC-CTFC information indicates which TFCs are mapped to which CTFCs.
Referring to FIG. 5C, if TFC 0 is mapped to CTFC 0, TFC 0 is a combination of TF 0 for DCH 1, TF 0 for DCH 2, and TF 0 for DCH 3. If TFC 5 is mapped to CTFC 7, TFC 5 is a combination of TF 1 for DCH 1, TF 0 for DCH 2, and TF 1 for DCH3. The TFC-CTFC mapping information is signaled for each TFC. If 8 TFCs are used as illustrated in FIG. 5C, the individual CTFCs mapped to the TFCs are signaled.
The above TFC-CTFC mapping information signaling is effective for a small number of TFCs. However, as more TFCs are used, the amount of the TFC-CTFC mapping information is increased. As a result, signaling load increases.
Accordingly, there is a need for an improved method and apparatus for reducing signaling load when configuring TFCs.